A photodiode (also referred to as “photodetector”) is a type of a sensor capable of converting light into current or voltage. Generally, the photodiode is a semiconductor device with a PIN or PN connection structure. When a photon of sufficient energy strikes the photodiode, it excites electrons, creating free electrons and positively charged electron holes. The holes move toward the anode, and electrons toward the cathode, and a photocurrent is produced proportional to the amount of incident light on the photodiode.
Other types of sensors include e.g. pyro-electric, piezo-electric, or capacitive sensors.
All of these sensors are common in that they include a pair of electrodes and, when stimulated by their respective stimuli, the state of charge across the electrodes changes. Current resulting from the changed state of charge across the electrodes can then be used to detect and quantify the stimuli. For example, a photodiode produces a change in the state of charge across its electrodes when the light is incident on the photodiode. In other words, the photodiode generates current (which may be referred to as “photocurrent”) in the presence of light, where the current is proportional to the amount of light incident on the photodiode. Similarly, a pyro-electric sensor produces a change in the state of charge across its electrodes when heated or cooled, a piezo-electric sensor produces a change in the state of charge across its electrodes in response to the change in its mechanical orientation (e.g. strain), while a capacitive sensor is one where changes in the environment change the effective capacitance of the sense element, which in turn changes the capacity to hold charge.
For such sensors, as well as other sensors operating according to similar principles of detecting change of charge state, it may be desirable to be able to detect and quantify stimuli originating from a specific source of interest as well as stimuli originating from all other sources besides the source of interest. For example, in context of a photodiode, it may be desirable to detect and quantify a contribution to the current generated by the photodiode that is due to the detection of light generated by a particular light source of interest, e.g. a particular light emitting diode (LED), as well as to detect and quantify contribution to the photocurrent that is due to the detection of light generated by all other light sources besides this light source of interest.
Overview
Present disclosure relates to a current detection module capable of differentiating and quantifying contribution to a current signal generated by a sensor as a result of stimulation by a certain source of interest (target source) from contributions from sources other than the source of interest (ambient sources). As long as the contribution from the target source comprises a pulsed signal, the module synchronizes itself to the pulse(s) so that there is a predetermined phase relationship between the pulse(s) and functions carried out by various stages of the module. The module may be re-used to also provide high precision detection and quantification of contributions to the sensor-generated current signal from ambient sources by presenting, to the current detection module, the contributions from ambient sources as one or more pulses which, in turn, trigger synchronization of the module. To that end, a detection system is provided that implements the current detection module as described herein and allows mode switching where, depending on the mode of operation being selected, the current detection module is configured to perform different kinds of measurements.
Accordingly, in one aspect of the present disclosure, a detection system includes a sensor configured to generate a current signal, where the current signal includes at least a first portion comprising a contribution to the current signal from a predefined source (i.e. a source of interest) and/or a second portion comprising a contribution to the current signal from one or more sources other than the predefined source, such other sources referred to herein as “ambient sources.” The detection system further includes a current detection module configured to receive the current signal generated by the sensor and generate a digital value indicative of the first portion of the current signal and/or a digital value indicative of the second portion of the current signal.
Furthermore, the detection system also includes a mode switch configured to set the current detection module to operate in at least one of a first mode, a second mode, and a third mode. In the first mode, the current detection module is synchronized to the predefined source and is configured to generate the digital value indicative of the first portion (i.e. current detection module is configured to detect the contribution to the current signal from the source of interest, while cancelling, reducing, or rendering below the noise of the current detection module the contribution to the current signal from sources other than the source of interest). In the second mode, the current detection module is configured to generate the digital value indicative of at least the second portion (i.e. the current detection module is configured to only detect the contribution to the current signal from the ambient sources) when the contribution to the current signal from the one or more sources other than the predefined source is in a first range of values. In the third mode, the current detection module is configured to generate the digital value indicative of at least the second portion (i.e. the current detection module is configured to only detect the contribution to the current signal from the ambient sources) when the contribution to the current signal from the one or more sources other than the predefined source is in a second range of values, the second range of values having an upper end higher than an upper end of the first range of values (i.e. ambient sources cause larger currents).
It should be noted that, in various embodiments, both the first and second portion need not always be present (e.g. the source of interest may be off, or there may be no or negligible amount of contributions from the ambient sources), and, if both present, not always do both need to be measured. Furthermore, in some embodiments of the second and third modes, the current detection module may be configured to generate the digital value indicative of not only the second portion but also the first portion (i.e. the current detection module is configured to detect the contribution to the current signal both from the source of interest and ambient sources).
As will be appreciated by one skilled in the art, aspects of the present disclosure may be embodied in various manners—e.g. as a method, a system, a computer program product, or a computer-readable storage medium. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Functions described in this disclosure may be implemented as an algorithm executed by one or more processing units, e.g. one or more microprocessors, of one or more computers. In various embodiments, different steps and portions of the steps of each of the methods described herein may be performed by different processing units. Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s), preferably non-transitory, having computer readable program code embodied, e.g., stored, thereon. In various embodiments, such a computer program may, for example, be downloaded (updated) to the existing devices and systems (e.g. to the existing current detection modules or controllers of such modules, etc.) or be stored upon manufacturing of these devices and systems.
Other features and advantages of the disclosure are apparent from the following description, and from the claims.